Rare-Earth Magnet Surface Gradient for Corrosion Resistance
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Solution Overview
Problem
Rare-earth magnets with protective layers suffer from incomplete corrosion resistance due to steam penetration under high-temperature, high-humidity environments, leading to accelerated corrosion within the magnet matrix.
Innovation Solution
A rare-earth magnet with a Cu and Co concentration gradient on its surface, where Cu and Co concentrations are higher on the surface than the inside, and optionally an Al gradient, inhibiting hydrogen occlusion in R-rich phases at grain boundaries, thereby enhancing corrosion resistance. The magnet may also include an R-rich phase with Cu, Co, and Al at grain-boundary triple junctions, suppressing hydrogen occlusion and improving corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protective layers are formed on the surface of rare-earth magnets, then corrosion resistance is improved, but steam penetrates through the protective layers under high-temperature high-humidity environment causing incomplete corrosion resistance
Solution Approach 1:
The patent applies local quality by creating a concentration gradient of Cu and Co elements where the surface region has higher concentrations compared to the interior. This gradient structure provides enhanced corrosion resistance at the surface (where steam contact occurs) while maintaining the magnetic properties in the interior region, thus resolving the contradiction between corrosion protection and steam penetration resistance.
Solution Approach 2:
The patent changes the concentration parameters of Cu and Co elements from uniform distribution to gradient distribution. By controlling the concentration of these elements to decrease from surface to interior, the patent achieves both surface protection against corrosion and maintenance of bulk magnetic properties, effectively addressing the steam penetration issue through protective layers.
2Reliability
If Cu and Co concentrations are increased on the surface to improve corrosion resistance, then hydrogen occlusion in R-rich phases is inhibited, but magnetic characteristics may be affected
Solution Approach 1:
The patent applies local quality by concentrating Cu and Co elements specifically in the surface region while keeping the interior composition suitable for magnetic properties. This spatial differentiation allows the surface to provide corrosion protection and inhibit hydrogen occlusion, while the interior maintains the R-T-B phase structure necessary for magnetic characteristics.
Solution Approach 2:
The patent changes the concentration parameters of Cu and Co from uniform to gradient distribution, with concentrations decreasing from surface to interior. This parameter optimization ensures sufficient Cu and Co content at the surface to inhibit hydrogen occlusion and improve corrosion resistance, while maintaining appropriate element ratios in the interior for preserving magnetic properties.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The described approach significantly enhances the corrosion resistance of rare-earth magnets while maintaining sufficient magnetic characteristics, allowing them to perform effectively over a long period, even in harsh environments.
Implementation Method 1
a Cu concentration distribution with a gradient along a direction from a surface of the rare-earth magnet to the inside thereof
Implementation Method 2
an Al concentration distribution with a gradient along a direction from the surface of the rare-earth magnet to the inside thereof
Data Source
AI summary
A rare-earth magnet is an R-T-B-based rare-earth magnet containing a rare-earth element R, a transition metal element T, and boron B. The rare-earth magnet further contains Cu and Co, while having a Cu concentration distribution with a gradient along a direction from a surface of the rare-earth magnet to the inside thereof, Cu having a higher concentration on the surface side of the rare-earth magnet than on the inside thereof, and a Co concentration distribution with a gradient along a direction from the surface of the rare-earth magnet to the inside thereof, Co having a higher concentration on the surface side of the rare-earth magnet than on the inside thereof. The rare-earth magnet is excellent in corrosion resistance.